Well, once again I come back to the PCV system, as that's the only way I could see oil getting there. As you get more blowby at high RPM/high boost, the inlet of the PCV system works in reverse, and oil vapor gets blown into the throttle body. This is normal operation, but if you have that much, there could be something else wrong, although I can't think what it would be.
I hate to sound like a broken record, but it's the only thing I can think ofIf you're pulling the SC off, I would blow compressed air through each of the PCV passages and see if you can detect any problems.